Dinosaurs Lived in Vast Ecological Zones
Don’t think of dinosaur species living in small ecological zones. Their habitats covered vast areas, according to a new study: “Researchers at McGill University are unlocking the mysteries of the little-known habits of dinosaurs in discovering that the entire western interior of North America was likely once populated by a single community of dinosaurs,” reported Science Daily.
Dinosaurs in North America inhabited ecological niches comparable to those of mammals today. They were mobile and adaptable: “They were able to colonize and dominate the landscape over very large distances, and were not nearly as constrained as we might have once thought,” said Matthew Vavrek, a PhD student at McGill. The team compared “alpha diversity” (diversity within an area) to beta diversity (diversity between areas) and found that beta diversity was low – comparable to wide-ranging mammals. This speaks of homogeneous communities covering the entire Western interior.
The team recognized that they are “just beginning to scratch the surface of dinosaur ecology.” This initial study raises many new questions about gene flow, migration, and affects of the dinosaurs on other megafauna and plant communities.
To the extent the conclusions in this study are reliable, they raise interesting questions about climate as well. Today’s western interior is highly stratified into biomes characterized by temperature, rainfall, flora and fauna. There are deserts, riparian zones, grasslands, chaparral, arboreal forests, and timberline meadows. Does the presence of dinosaur species across nearly continent-sized regions indicate that the climate or geography was radically different in the past? If so, what would that imply about earth history as well as political debates over human impact on the environment? These are questions that can be posed, not answers we are proposing.
One needs to be cautious with concepts, techniques and inferences in studies like this. Some terms that are taken for granted in science become rather slippery when one has to pin them down. Take ecological niche, for instance, or predator. The differences between elements of these set can arguably outweigh the things they have in common. A wolf spider and a grizzly bear can both be considered predators, for instance, and a human and a bedbug can both inhabit the same ecological niche. Terms like these are useful for human theories and conversations. It is difficult to defend the notion that they refer to realities that are actually “out there” in the world, independent of human reasoning. To what does alpha diversity and beta diversity refer? Sounds Greek. The Greeks were humans, after all, not dinosaurs; although they were mammals.
The authors themselves admit that they are barely scratching the surface of dinosaur ecology. Let’s let them scratch some more. There can be surprises in lower layers. Maybe they are not even scratching the right surface.